The present invention is in the field of drive belt tensioning. In particular this invention is directed towards a compensating belt tensioner which is very useful for adjusting the tension on drive belts, especially timing belts.
During normal use drive belts commonly become slack due to belt stretching, machine vibration and/or heat. To keep the machine operating properly, these belts are subjected to regular belt tension adjustments.
In the present state of the art, drive belts are normally tensioned by one of three methods. One method is to move the drive motor or one of the drive points to take up belt slack. This however is not always practical, and some sort of tension gage should be used to verify the tension. Another method is a spring-loaded tensioner, which is loosened to take up belt slack, and then tightened down. Unfortunately, because the spring length changes (An extension spring would become shorter, a compression spring would become longer, and a torsion spring would become more angularilly relaxed.), with each adjustment, its tension force decreases, and therefore each adjustment leaves the drive belt with slightly less tension than the time before. A third method is to have an active, xe2x80x9clivexe2x80x9d, tensioner which is also spring loaded, (usually powered by a torsion spring) but the spring is not tightened down, and is therefore free to continuously take up the slack in the drive belt. This method is not recommended for timing belts, as the tensioner can recoil under transient loads, allowing belt tooth cogging, and resultant machine malfunction.
A drive belt tensioner method and assembly are desired which is not active, which can adjust the tension of the drive belt simply, and efficiently, and which will apply a consistent, predictable belt tensioning setting, regardless of belt age or machine configuration tolerances.
A compensating tensioner assembly, and a method for tensioning drive belts on machines wherein a base plate is mounted to the machine at a base plate mounting point such that the base plate can be rotated about the base plate mounting point when the base plate is not secured against rotation. A tensioner arm is then mounted to the base plate at a tensioner arm mounting point such that the tensioner arm can be rotated about the tensioner arm mounting point when the tensioner arm is not secured against rotation and wherein a belt tensioning pulley is mounted to the tensioner arm such that it is adjacent to the drive belt.
A spring with an end one and an end two, is attached at end one to the base plate, and at end two to the tensioner arm, such that when the tensioner arm is not secured against rotation the spring causes the tensioner arm to pivot about the tensioner arm mounting point, which in turn causes the belt tensioning pulley to exert a force on the drive belt in a manner which increases the tension on the drive belt, the spring having a predetermined working length, at which the spring causes a predetermined tension to be applied on the drive belt.
The base plate is then rotated about the base plate mounting point, and the tensioner arm about the tensioner arm mounting point until the spring attains the predetermined working length. Both the base plate and the tensioner arm are then secured against rotation.